share_nfs

- make local NFS file systems available for mounting by remote systems

Synopsis

share [-ddescription] [-F nfs] [-ospecific_options] pathname

Description

The share utility makes local file systems available for mounting by remote
systems. It starts the nfsd(1M) and mountd(1M) daemons if they are not
already running.

If no argument is specified, then share displays all file systems currently
shared, including NFS file systems and file systems shared through other distributed
file system packages.

Options

The following options are supported:

-ddescription

Provide a comment that describes the file system to be shared.

-Fnfs

Share NFS file system type.

-ospecific_options

Specify specific_options in a comma-separated list of keywords and attribute-value-assertions for interpretation by the file-system-type-specific command. If specific_options is not specified, then by default sharing is read-write to all clients. specific_options can be any combination of the following:

aclok

Allows the NFS server to do access control for NFS Version 2 clients (running SunOS 2.4 or earlier). When aclok is set on the server, maximal access is given to all clients. For example, with aclok set, if anyone has read permissions, then everyone does. If aclok is not set, minimal access is given to all clients.

anon=uid

Set uid to be the effective user ID of unknown users. By default, unknown users are given the effective user ID UID_NOBODY. If uid is set to -1, access is denied.

index=file

Load file rather than a listing of the directory containing this file when the directory is referenced by an NFS URL.

log=tag

Enables NFS server logging for the specified file system. The optional tag determines the location of the related log files. The tag is defined in etc/nfs/nfslog.conf. If no tag is specified, the default values associated with the globaltag in etc/nfs/nfslog.conf is used. Support of NFS server logging is only available for NFS Version 2 and Version 3 requests.

nosub

Prevents clients from mounting subdirectories of shared directories. For example, if /export is shared with the nosub option on server fooey then a NFS client cannot do:

mount -F nfs fooey:/export/home/mnt

NFS Version 4 does not use the MOUNT protocol. The nosub option only applies to NFS Version 2 and Version 3 requests.

nosuid

By default, clients are allowed to create files on the shared file system with the setuid or setgid mode enabled. Specifying nosuid causes the server file system to silently ignore any attempt to enable the setuid or setgid mode bits.

public

Moves the location of the public file handle from root (/) to the exported directory for WebNFS-enabled browsers and clients. This option does not enable WebNFS service; WebNFS is always on. Only one file system per server may use this option. Any other option, including the -ro=list and -rw=list options can be included with the public option.

ro

Sharing is read-only to all clients.

ro=access_list

Sharing is read-only to the clients listed in access_list; overrides the rw suboption for the clients specified. See access_list below.

root=access_list

Only root users from the hosts specified in access_list have root access. See access_list below. By default, no host has root access, so root users are mapped to an anonymous user ID (see the anon=uid option described above). Netgroups can be used if the file system shared is using UNIX authentication ( AUTH_SYS).

rw

Sharing is read-write to all clients.

rw=access_list

Sharing is read-write to the clients listed in access_list; overrides the ro suboption for the clients specified. See access_list below.

sec=mode[:mode]. . .

Sharing uses one or more of the specified security modes. The mode in the sec=mode option must be a node name supported on the client. If the sec= option is not specified, the default security mode used is AUTH_SYS. Multiple sec= options can be specified on the command line, although each mode can appear only once. The security modes are defined in nfssec(5).

Each sec= option specifies modes that apply to any subsequent window=, rw, ro, rw=, ro= and root= options that are provided before another sec=option. Each additional sec= resets the security mode context, so that more window=,rw,ro,rw=,ro= and root= options can be supplied for additional modes.

sec=none

If the option sec=none is specified when the client uses AUTH_NONE, or if the client uses a security mode that is not one that the file system is shared with, then the credential of each NFS request is treated as unauthenticated. See the anon=uid option for a description of how unauthenticated requests are handled.

secure

This option has been deprecated in favor of the sec=dh option.

window=value

When sharing with sec=dh, set the maximum life time (in seconds) of the RPC request's credential (in the authentication header) that the NFS server allows. If a credential arrives with a life time larger than what is allowed, the NFS server rejects the request. The default value is 30000 seconds (8.3 hours).

access_list

The access_list argument is a colon-separated list whose components may be any
number of the following:

hostname

The name of a host. With a server configured for DNS or LDAP naming in the nsswitch “hosts” entry, any hostname must be represented as a fully qualified DNS or LDAP name.

netgroup

A netgroup contains a number of hostnames. With a server configured for DNS or LDAP naming in the nsswitch “hosts” entry, any hostname in a netgroup must be represented as a fully qualified DNS or LDAP name.

domain name suffix

To use domain membership the server must use DNS or LDAP to resolve hostnames to IP addresses; that is, the “hosts” entry in the /etc/nsswitch.conf must specify ”dns” or ”ldap” ahead of ”nis” or ”nisplus”, since only DNS and LDAP return the full domain name of the host. Other name services like NIS or NIS+ cannot be used to resolve hostnames on the server because when mapping an IP address to a hostname they do not return domain information. For example,

NIS or NIS+ 172.16.45.9 --> "myhost"

and

DNS or LDAP 172.16.45.9 -->
"myhost.mydomain.mycompany.com"

The domain name suffix is distinguished from hostnames and netgroups by a prefixed dot. For example,

rw=.mydomain.mycompany.com

A single dot can be used to match a hostname with no suffix. For example,

rw=.

matches ”mydomain” but not ”mydomain.mycompany.com”. This feature can be used to match hosts resolved through NIS and NIS+ rather than DNS and LDAP.

network

The network or subnet component is preceded by an at-sign (@). It can be either a name or a dotted address. If a name, it is converted to a dotted address by getnetbyname(3SOCKET). For example,

=@mynet

would be equivalent to:

=@172.16 or =@172.16.0.0

The network prefix assumes an octet-aligned netmask determined from the zeroth octet in the low-order part of the address up to and including the high-order octet, if you want to specify a single IP address (see below). In the case where network prefixes are not byte-aligned, the syntax allows a mask length to be specified explicitly following a slash (/) delimiter. For example,

=@theothernet/17 or =@172.16.132/22

...where the mask is the number of leftmost contiguous significant bits in the corresponding IP address.

When specifying individual IP addresses, use the same @ notation described above, without a netmask specification. For example:

=@172.16.132.14

Multiple, individual IP addresses would be specified, for example, as:

root=@172.16.132.20:@172.16.134.20

A prefixed minus sign (-) denies access to that component of access_list.
The list is searched sequentially until a match is found that either
grants or denies access, or until the end of the list is
reached. For example, if host ”terra” is in the ”engineering” netgroup, then

rw=-terra:engineering

denies access to terra but

rw=engineering:-terra

grants access to terra.

Operands

The following operands are supported:

pathname

The pathname of the file system to be shared.

Examples

Example 1 Sharing A File System With Logging Enabled

The following example shows the /export file system shared with logging enabled:

example% share -o log /export

The default global logging parameters are used since no tag identifier is
specified. The location of the log file, as well as the necessary
logging work files, is specified by the global entry in /etc/nfs/nfslog.conf. The
nfslogd(1M) daemon runs only if at least one file system entry in
/etc/dfs/dfstab is shared with logging enabled upon starting or rebooting the system.
Simply sharing a file system with logging enabled from the command line does
not start the nfslogd(1M).

See Also

Notes

If the sec= option is presented at least once, all uses of
the window=,rw,ro,rw=,ro= and root= options must come after
the first sec= option. If the sec= option is not presented, then
sec=sys is implied.

If one or more explicit sec= options are presented, sys must appear
in one of the options mode lists for accessing using the AUTH_SYS
security mode to be allowed. For example:

share-Fnfs /varshare-Fnfs-osec=sys /var

grants read-write access to any host using AUTH_SYS, but

share-Fnfs-osec=dh /var

grants no access to clients that use AUTH_SYS.

Unlike previous implementations of share_nfs, access checking for the window=, rw, ro, rw=, and ro=
options is done per NFS request, instead of per mount request.

Combining multiple security modes can be a security hole in situations where
the ro= and rw= options are used to control access to weaker
security modes. In this example,

share-Fnfs-osec=dh,rw,sec=sys,rw=hosta /var

an intruder can forge the IP address for hosta (albeit on each
NFS request) to side-step the stronger controls of AUTH_DES. Something like:

share-Fnfs-osec=dh,rw,sec=sys,ro /var

is safer, because any client (intruder or legitimate) that avoids AUTH_DES only
gets read-only access. In general, multiple security modes per share command should
only be used in situations where the clients using more secure modes
get stronger access than clients using less secure modes.

If rw=, and ro= options are specified in the same sec= clause,
and a client is in both lists, the order of the two
options determines the access the client gets. If client hosta is in
two netgroups - group1 and group2 - in this example, the client
would get read-only access:

share-Fnfs-oro=group1,rw=group2 /var

In this example hosta would get read-write access:

share-Fnfs-orw=group2,ro=group1 /var

If within a sec= clause, both the ro and rw= options are
specified, for compatibility, the order of the options rule is not enforced.
All hosts would get read-only access, with the exception to those in
the read-write list. Likewise, if the ro= and rw options are specified, all
hosts get read-write access with the exceptions of those in the read-only
list.

The ro= and rw= options are guaranteed to work over UDP and
TCP but may not work over other transport providers.

The root= option with AUTH_SYS is guaranteed to work over UDP and
TCP but may not work over other transport providers.

The root= option with AUTH_DES is guaranteed to work over any transport
provider.

There are no interactions between the root= option and the rw, ro, rw=, and
ro= options. Putting a host in the root list does not override
the semantics of the other options. The access the host gets is
the same as when the root= options is absent. For example, the following
share command denies access to hostb:

share-Fnfs-oro=hosta,root=hostb /var

The following gives read-only permissions to hostb:

share-Fnfs-oro=hostb,root=hostb /var

The following gives read-write permissions to hostb:

share-Fnfs-oro=hosta,rw=hostb,root=hostb /var

If the file system being shared is a symbolic link to a
valid pathname, the canonical path (the path which the symbolic link follows)
are shared. For example, if /export/foo is a symbolic link to /export/bar
(/export/foo -> /export/bar), the following share command results in /export/bar as the shared pathname (and
not /export/foo).

example# share-Fnfs /export/foo

An NFS mount of server:/export/foo results in server:/export/bar really being mounted.

This line in the /etc/dfs/dfstab file shares the /disk file system read-only
at boot time:

share-Fnfs-oro /disk

The same command entered from the command line does not share the
/disk file system unless there is at least one file system entry
in the /etc/dfs/dfstab file. The mountd(1M) and nfsd(1M) daemons only run if
there is a file system entry in /etc/dfs/dfstab when starting or rebooting the
system.

The mountd(1M) process allows the processing of a path name the contains
a symbolic link. This allows the processing of paths that are not
themselves explicitly shared with share_nfs. For example, /export/foo might be a symbolic link
that refers to /export/bar which has been specifically shared. When the client
mounts /export/foo the mountd processing follows the symbolic link and responds with the
/export/bar. The NFS Version 4 protocol does not use the mountd processing
and the client's use of /export/foo does not work as it does
with NFS Version 2 and Version 3 and the client receives an error
when attempting to mount /export/foo.